This application claims the priority of Korean Patent Application No. 2002-3193, filed on Jan. 19, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a fiat lamp with horizontal facing electrodes, and more particularly, to a flat lamp with horizontal facing electrodes, in which electrodes are disposed on front and rear substrates in such a way that the electrodes on the front substrate do not face the electrodes on the rear substrate, and accordingly stable discharging occurs and brightness increases.
2. Description of the Related Art
Flat lamps for use as a backlight of a liquid crystal display (LCD) have been developed from conventional light-edging or light-directing cold cathode fluorescent lamps to surface discharging type or facing surfaces discharging type plasma lamps. The surface discharging type or facing surfaces discharging type plasma lamps are considered and developed in that the entire space under a light emitting diode serves as a discharging space in order to achieve luminous efficiency, the uniformity of luminescent brightness, or the like.
Surface discharging type plasma lamps generally provide more stable discharge characteristics than facing surfaces discharging type plasma lamps, but the brightness of the former lamps is lower than that of the latter lamps. In an example of a conventional surface discharging flat lamp (see M. Ilmer et al., Society for Information Display International Symposium, Digest of Technical Papers 31, 931 (2000)), an entire discharging area is divided into many fine discharging areas in order to prevent local concentration of discharge, and stable discharging can be performed. However, since the uniformity of the entire luminescent brightness is not good due to the difference in the luminescent brightness between fine discharging areas and the gap therebetween, this lamp must adopt a diffuser sheet to evenly diffuse light.
FIG. 1 shows another example of a conventional surface discharging flat lamp. A discharging space, which is filled with a discharge gas, is formed between front and rear substrates 1 and 2 spaced apart from each other by a wall 7. Discharging electrodes 3 and 4 are formed at both sides on the inner surface of the rear substrate 2 and each has a dielectric layer 5 formed thereon. A fluorescent layer 6 is formed on the inner surface of each of the front and rear substrates 1 and 2. It is known (see Y. Ikeda et al., Society for Information Display International Symposium, Digest of Technical Papers 31, 938 (2000)) that a surface discharging type flat lamp having such a structure provides low brightness according to the discharge characteristics.
FIG. 2 shows an example of a conventional facing surfaces discharging type flat lamp. A wall 7a isolates a front substrate 1a from a rear substrate 2a by a predetermined interval such that a discharging space is formed between the front and rear substrates 1a and 2a. Discharging electrodes 3a and 4a are formed on the outer surface of the front substrate 1a and the inner surface of the rear substrate 2a, respectively, such that the discharging electrodes 3a and 4a face each other. A dielectric layer 5a is formed on the electrode 4a, and a fluorescent layer 6b is formed on the electrode 4a and on the inner surface of the front substrate 1a. Such a facing surfaces discharging type flat lamp (see J. Y. Choi et al., Proceedings of the 1st International Display Manufacturing Conference, 231(2000)) provides a higher brightness than the surface discharging flat lamp of FIG. 1. However, this lamp has a low discharge efficiency due to excessive flowing of current and performs unstable discharging.
FIG. 3 shows another example of a conventional facing surfaces discharging type flat lamp. Electrodes 3b and 4b are formed on the inner surfaces of facing walls 7b so as to face each other. Each of the electrodes 3b and 4b is protected by a dielectric layer 5b. Also, the facing walls 7b separate the front and rear substrates 1b and 2b from each other such as to form a discharging space between the electrodes 3b and 4b. A fluorescent layer 6b is formed on each of the inner surfaces of the front and rear substrates 1b and 2b. A facing surfaces discharging type flat lamp having facing electrodes at a wall can prevent over-flowing of current, but is prone to have an unstable performance, and particularly, local discharging.
To sum up, conventional flat lamps provide low brightness if they perform stable discharging. Alternatively, if they have a high brightness, they suffer unstable discharging.